Chemically prepared wood pulp product and process for producing the same



Patented July 8, 1947 CHEMICALLY PREPARED WOOD PULP PRODUCT AND PROCESSFOR PRO DUCING THE SALE Paul Henry Schlosser and Kenneth Russell Gray,

Shelton, W'ash., assignors' to Rayonier Incorporated, Shelton DelawareWash., a corporation of No Drawing. Application May 3, 1944, Serial No.533,929

9 Claims. 1

This invention relates to the production of cellulosic products, and hasfor its general object the provision of certain improvements in carryingout one or more of the processing steps in the production of suchproducts. Theinvention is of special advantage in the preparation andprocessing of viscose derived from chemically prepared wood pulp, and inthis connection aims to improve the steps of shredding, filtering andspinning viscose. The invention further contemplates, as a new articleof manufacture, a chemically prepared wood pulp product havingincorporated therein a mixed ether obtainable by resoda to form thesolution commonly known as viscose, which is opacified if desired,filtered, and

acting ethylene oxide with a rosin alcohol. (Such such cellulosicproducts as rayon and other synthetic fibers, nitrocellulose, celluloseacetate, cellulose ethers, Cellophane and similar cellulosic films orsheets, etc. Wood pulp is commonly prepared and marketed in sheet form,and comminution or shredding is customarily one of the initial steps inits subsequent processing. When wood pulp is used in bulk form, eitherwet or dry, shredding or comminution is frequently a step involvedin'the subsequent processing. Since such subsequent processing usuallyinvolves the conversion of the cellulose of the wood pulp to somecellulose derivative and the solution of the derivative in a. suitablesolvent, the purpose oi. shredding is to break down the sheet into afluffy mass or crumb in which the individual fibers will be suitablyexposed to the action of the derivative-forming reagent or reagents.Thus, for example, in the production of viscose the wood pulp sheet iscustomarily steeped in a caustic soda solution to form alkali cellulose,and the alkali cellulose, after pressing and while still in sheet form,is shredded or comminuted to properly prepare the cellulose fibers forthe xanthating reaction with carbon bisulflde. The resulting sodiumcellulose xanthate is dissolved in dilute caustic spun into filaments.

Normal dissolving wood pulps in present use consist mainly of cellulose,but contain appreciable amounts of non-cellulosic impurities, such ashemi-celluloses, fats, resins, waxes, etc. One of the main objects inthe manufacture of a highly refined dissolving pulp is to remove as muchas possible of the non-cellulosic impurities, so that a whiter, purerpulp results, which is capable, in the manufacture of rayon, ofproducing a higher grade yarn.

We find,'however, that not all of the noncellulosic impurities which canbe removed are undesirable, and, in fact, certain of such impurities,normally present in small amounts, are highly beneficial in aiding theprocessing of the pulp into viscose, especially as regards the step ofshredding the alkali cellulose. These beneficial impurities which aidthe shredding operation are probably of the nature of fiber lubricantswhich permit the steeped and pressed pulp to be thoroughly shredded intoa fiufiy condition more readily and without mechanical damage to thealkali cellulose fibers which would cause them to react incompletelywith carbon bisulphide. In a pulp which has not been highly refined,most of these beneficial impurities constitute a portion of thematerials removable by organic solvents, as, for example, ether,benzene, alcohol, etc. These beneficial impurities, often loosely termedresins, are mainly of the nature of waxes, fats and resins, the latteroften being present in a relatively small amount.

In theory, the problem of making a good pulp could be solved by removingall the undesirable impurities while retaining those impurities whichfacilitate the shredding operation by lubricating the fibers orotherwise. In practice, such a cleancut separation is difflcult toaccomplish directly.

We have discovered that better results are obtainable by removing mostor all of the impurities including those which serve beneficially aslubricants to the alkali cellulose fibers during shredding, and thenadding to the pulp or to the alkali cellulose prior to the completion ofshredding a sufficient amount of an agent capable of acting like, andactually being more eiiective than, the natural beneficial impurities,

White, highly purified or refined wood pulps are very advantageous torthe production of high grade rayon yarns of superior strength and color,and forthis reason, are highly esteemed by the trade. Such highlyrefined pulps are in general characterized by having an ether extract ofabout 0.15% or less where such values refer to the amount of naturalether extractable material left in the pulp after the purificationprocesses. While our invention is particularly applicable to such highlyrefined pulps containing not more than about 0.15% of ether extractablematerial, it may be applied with certain advantages to the processing ofnormal dissolving pulps containing substantially more than 0.15% ofether extractable material, although such pulps do not generally yieldthe highest grade yarns and their processing into shredded alkalicellulose is not accompanied byany particular difficulty.

We have discovered a class of agents, namely, mixed ethers of rosinalcohols, which lubricate or protect the alkali cellulose fibers duringshredding, and which are chemically entirely different from thebeneficial impurities naturally present in the pulp. These agents aresoluble or readily dispersible in water. In general, they are much moreefiecti've in promoting shredding than the beneficial impuritiesnaturally present in the pulp. Moreover, these agents exercise abeneficial infiuence upon certain subsequent steps in the preparationand processing of viscose into rayon which the natural beneficialimpurities do not exercise. Based on these discoveries, our inventioninvolves improving one or more of the processing steps in the productionof cellulosic products from chemically prepared wood pulp by carryingout one or more of the processing steps in the presence of a mixed etherof a rosin alcohol. When applied to the preparation and processing ofviscose derived from chemically prepared wood pulp, the inventionparticularly involves carrying out the shredding oi the alkalicellulose, or at least the final stage of shredding, and the spinning ofthe viscose in the presence or a mixed ether of a rosin alcohol. Wherethe invention is practiced solely to improve the spinning of theviscose, it is immaterial from what cellulosic raw material the viscoseis derived.

The compounds of the invention are mixed ethers at least dispersible inand. preferably substantially soluble in water which are obtainable byreacting ethylene oxide with a rosin alcohol. As used herein, a rosinalcohol means an alcohol derived by reduction of rosinor abietic acidand consisting of dihydroabietyl, dehydroabietyl, tetrahydroabietyl orabietyl alcohol. More particularly, the compounds are mixed etherscontaining a polyethylene oxide radical and a cycloaliphatic hydrocarbonradical derived from abietic acid and selected from the group consistingof the dihydroabietyl, dehydroabietyl, tetrahydroabietyl, and abietylradicals.

Suitable compounds at least water dispersible will be mixed etherscontaining a polyethylene oxide radical with at least three ethenoxyresidues and a cycloaliphatic hydrocarbon radical selected from thegroup consisting of dihydroabietyl, dehydroabietyl, andtetrahydroabietyl and abietyl radicals. In regard to effectiveness thereis apparently no practical upper limit for the number of ethenoxy units.The most preferred compounds, however, are mixed ethers containing apolyethylene oxide radical with from 6-20 ethenoxy units and acycloaliphatic hydrocarbon radical selected Irom the group consisting 4of the dihydroabietyl, dehydroabietyl, tetrahydroabietyl, and abietylradicals.

In preparing the mixed ethers of the invention, it is not necessary touse pure rosin alcohols. We have had very good results by condensingethylene oxide with the mixture of rosin alcohols, commonly sold underthe name Hydroabietyl Alcohol, and which consists chiefly of a mixtureof dihydroabietyl, dehydroabietyl, tetrahydroabietyl and abietylalcohols. Examples of specific products are products obtained bycondensing approximately 3, 4, 6, 12, 20 and 160 mols of ethylene oxiderespectively per average molecular weight of the rosin alcohol mixtureknown as Hydroabietyl Alcohol. The condensation is brought about by anyof the normal methods for reacting ethylene oxide with an alcohol,preferably incorporating an alkali as catalyst with the alcohol.Suitable methods include either adding a small proportion of 48% NaOH ordissolving metallic sodium in the heated rosin alcohol.

While highly refined wood pulps are advantageous for the production ofhigh grade rayon yarns of superior strength and color, the reaction ofthe shredded alkali cellulose from such pulps with carbon bisulphide isfrequently incomplete.

This impairment in the xanthating activity of the shredded alkalicellulose is due to some damage to the fibers during the shreddingoperation or to incomplete comminution or to formation of compressedfiber bundles. In the case of the conventional shredder having revolvingblades coacting with a stationary saddle bar, the tendency for suchdamage is especially great if the clearance between the revolving bladesand the saddle bar is a little less than the correct value. In anextreme case, with a very highly refined pulp, shredding, even underoptimum conditions, may produce a shredded pulp which xanthates lesscompletely than if the alkali cellulose were not shredded at all. Inother cases, it is possible to obtain reasonably satisfactory shreddingof the alkali cellulose from highly refined pulps by adjusting theshredder clearance and by experimenting to find the optimum shreddingtime for the particularpulp and particular shredder. In this manner itis possible in some cases to obtain 1 almost as complete a degree ofxanthation of the shredded alkali cellulose from a highly refined pulpas would be obtained with the shredded alkali cellulose from a less purepulp. But the necessity of constant supervision and adjustment to assureoptimum shredding conditions makes the shredding of highly refined pulpstoo sensitive for satisfactory commercial practice. This sensitivity todamage during shredding of the alkali cellulose from highly refinedpulps is overcome, in our invention, by carrying out the shreddingoperation in the presence of a mixed ether of a rosin alcohol which maybe added to the pulp prior to shredding or to the alkali cellulose priorto the completion of shredding. While the invention thus improves theshredding operation, the most note-worthy evidence of this improvementis in the subsequent filtration of the viscose. The improvement inshredding produces a shredded alkali cellulose which reactssubstantially completely with carbon bisulphide, and the resultinviscose is comparatively free of unreacted fibers and filtrationproceeds more rapidly and economically.

In the spinning of viscose into acid spin baths containing certainmetallic salts and especially a zinc salt, incrustations tend to formwithin the orifices of the spinneret, either partially or completelyblocking the orifices. The partial blocking of the orifices causesobjectionable irregularities in the thickness of the filaments andfrequently causes breaking of the filaments which necessitatesinterruption of the spinning operation to change spinnerets. Theformation of such incrustations is suppressed or minimized in thepresent invention by carrying out the spinning operation in the presenceof a mixed ether of a rosin alcohol. The mixed ether may be added to theviscose or to the constituents entering into the production of theviscose, or may be added to the acid spin bath. While this aspect of ourinvention relates particularly to improving spinduction of this product,as .a

' When the agent is so incorporated in the wood 1 pulp, by themanufacturer thereof, the pulp ning. conditions in the viscose processwhere I viscose is normally extruded through spinnerets or otherorifices into acid setting baths, it is to be understood that theinvention is not limited to the viscose process. but is applicable toany process where cellulosic solutions are extruded through spinneretsor other orifices into aqueous setting baths where incrustations tend toform within the extrusion orifices. In such cases, the 1 invention isonly subject to the limitations that the material be added in such a wayas to be present in either the spinning solution or spin bath at thetime of spinning.

When a mixed ether of the invention has been employed to improveshredding, in accordance with the invention, the mixed ether will bepresent in the resulting viscose. Although, as hereinafter moreparticularly explained, th amount oi mixed ether required for securingthe contemplated improvement in suppressing or minimizing the formationof incrustations during spinning is slightly greater than the amountrequired for securing the contemplated improvement in shredding andfiltration, there is no objection to carrying out the shredding step inthe presence of such amount of said mixed ether as is required in thespinning of the viscose. Indeed, the full advantages of our inventionare best realized when a mixed ether of the invention is added to thealkali cellulose prior to the completion of shredding and in amountadequate for securing the contemplated improvement in spinning theviscose.

The most practical and economical manner of securing the desiredpresence of a mixed'ether of a rosin alcohol during ,the shredding ofthe alkali cellulose and during the spinning of the viscose is toincorporate such a mixed ether in the wood pulp. This may beadvantageously effected by adding the mixed ether to the pulp on thesheet-forming machine subsequent to sheet formation but prior tocomplete drying, by spraying the pulp sheet with an aqueous solution ofthe mixed ether or bymeans of a rotating roll partly immersed in such a.solution. If desired,

the mixed ether of a rosin alcohol may be incorporated in the pulp priorto sheet formation, as, for example, by adding the agent to a suspensionof pulp in water in a stock chest. In the latter case, the white watershould preferably be recirculated in order to prevent considerable lossof the agent when eliminatin water in sheet formation. In any case,there is produced a chemically prepared wood pulp product havingincorporated therein a mixed ether containing a polyethylene oxideradical with at comes to the rayon manufacturer in a form' calculated tosecure the full advantages of the invention in the preparation andprocessing of the viscose into high grade rayon yams.

The amount of the said mixed ethers used in the practice of theinvention is relatively small, ranging from 0.01 to 0.25%, by weight onthe bone dry weight of the wood pulp used, when.

the agent is incorporated in or added to the pulp or to the viscose. Sofar as the objectives of the invention are concerned, there is little,if

any, improvementby increasing the amount of the mixed ethers above0.25%, and such higher amounts give rise to certain disadvantages. Thesedisadvantages include the causing of excessive softness in the sheetresulting in mechanical difllculties in steeping, excessiveballformation in xanthation, difilculties in the dissolving operationdue both to the excessive ball formation in the xanthating step and dueto excessive foaming in the viscose solution. Also, there will beconsiderable dlfllculty in obtaining a completely deaerated viscosewhich is absolutely necessary for satisfactory spinning. Higherconcentrations of the mixed ethers also unduly lower least threeethenoxy residues and a cycloaliphatic the surface tension of theviscose, thus changing the coagulating conditions so that the viscosecannot be satisfactorily spun by standard The amount of the mixed etherof a rosin alcohol required for securing the contemplated improvement inshredding' and filtration is generally slightly less than the amountrequired for securing the contemplated improvement in suppressing orminimizing the formation of incrus tations during spinning. Thus, thecontemplated improvement in shredding and filtration will generally bebroughtabout by from 0.02% to 0.05% of the mixed ether, and rarely wouldmore than 0.1% be required. For suppressing or minimizing the formationof incrustations, the mixed ether should be present in the viscose inamount of at least 0.05% and often 0.1% or more. These percentagefigures are based on the bone-dry weight of the pulp used. When themixed ether is incorporated in the spin bath, the amount present inthespin bath may advantageously be 0.001 to 0.1% by weight on the weight ofthe bath.

While it is our preferred practice to 111001130? rate the mixed ether inthe wood pulp product, which preferably is a highly refined pulpcontaining not more than about 0.15% of ether extractable material andis commonly marketed in sheet form, the presence of the agent, duringthe processing steps of shredding, filtering, and

spinning may be secured in any other appropri-' the agent may be sprayedupon or otherwise suita ably added to all or a portion of the alkalicellulose prior to shredding or prior tothe completion of shredding.Finally, in those cases where the invention is not practiced in the.shredding and filtering steps, the mixed ether of I a rosin alcohol maybe incorporated in the vlsnew article of manufacture. is one of theaspects of the invention.

cose or the spin bath, and in such cases the suppressing and minimizingof the formation of incrustations will be attained where the viscose ismade of other cellulo sic raw materials as well as wood pulp. However,we believe it will generally be found more advantageous to incorporatethe mixed ether in the initial wood pulp product, both as a matter ofconvenience and economy in preparing and processing the viscose, andbecause a very uniform distribution of the agent throughout the pulp iseasily attained.

When the invention is practiced for effecting the hereinbefore-mentionedimprovements in shredding and filtering, certain further economies areeffected in the subsequent steps of xanthating,- dissolving andfiltering. In viscose solutions there is usually a certain amount ofundissolved fibers and gel-like material due to the incomplete reactionof the cellulose with the carbon bisulphide during xanthation. Prior tospinning, the viscose solutions are filtered several times to removethese gels and undissolved fibers. In the event that theviscosesolutions contain excessive amounts of undissolved and partiallydissolved fibers, filtration is an expensive operation. In such casesthe filters become rapidly clogged and the filter media must be changedfrequently in order that the Viscose will pass through in a reasonabletime. Frequent changing of the filter media is expensive not only asregards consumption of filter cloth but also in view of the veryconsiderable amount of labor involved and also since a certain amount ofviscose is lost every time the filter is opened up. Furthermore, whenthe viscose solutions contain very large proportions of gel-likematerial, filtration is usually not altogether satisfactory in that someof the smaller gel-like particlestend to pass through the pores of thecloth with adverse eflect upon the spinning operation. It has heretoforebeen the practice in the viscose industry, when processing pulps whichtend to yield viscose solutions high in undissolved material and havingpoor filtration properties, to minimize such difficulties by carryingout the xanthation with amounts of carbon bisulphide considerably inexcess of that normally required. Use of excess carbon bisulphide isex-' the shredding operation that the alkali cellulose subsequentlyreacts much more completely with carbon bisulphide and yields a viscosesolution very free from undissolved and partially dissolved celluloseparticles and having good filtration properties. This result can beaccomplished not only without the use of excess carbon bisulphide, butin many cases satisfactory viscose solutions can be obtained usingamounts of carbon bisulphide very substantially less than the amountsnormally required.

We claim:

1. The method of improving the processing of refined chemical pulpcontaining not more than 0.15% ether-extractable matter into viscosecomprising adding to one of the viscose forming materials a mixed etherhaving attached to the ether oxygen a polyethylene oxide radical with atleast three ethenoxy residues and a cycloaliphatic radical selected fromthe group consisting of the di- 8 hydroabietyl, dehydroabietyl,tetrahydroabietyl and abietyl radicals, said ether being added in anamount of from 0.01% to 0.25% by weight based on the weight of the bonedry pulp.

2. Th method of improving the processing of refined chemical pulpcontaining not more than 0.15% ether-extractable matter into viscosecomprising adding to one of the viscose forming materials a mixed etherhaving attached to the ether oxygen a polyethylene oxide radical withfrom 6 to 20 ethenoxy units and a cycloaliphatic radical selected fromthe group consisting of the dihydroabietyl, dehydroabietyl,tetrahydroabietyl and abietyl radicals, said ether being added in anamount of from 0.01% to 0.25% by weight based on the weight of the bonedry pulp.

3. In the processing of wood pulp into rayon by the viscose process, theimprovement which comprises adding to one of the viscose formingmaterials at a stage prior to completion of shredding from 0.01% to0.25% by weight based on the bone dry weight of the pulp of a mixedether having attached to the ether oxygen a polyethylene oxide radicalwith at least three ethenoxy residues and a c'ycloaliphatic radicalselected from the group consisting of the dihydroabietyl,dehydroabietyl, tetrahydroabietyl and abietyl radicals. r

4. In th processing of wood pulp into rayon by the viscose process, theimprovement which comprises carrying out at least one of the stepsconsisting of shredding, filtering and spinning in the presence of from0.01 to 0.25% by weight based on the bone dry weight of the pulp of anadded mixed ether having attached to the ether oxygen a polyethyleneoxide radical with at least three ethenoxy residues and a cycloaliphaticradical selected from the group consisting of the dihydroabietyl,dehydroabietyl, tetrahydroabietyl and abietyl radicals.

5. In the processing of wood pulp into rayon by the viscose process, theimprovement which comprises carrying out at least one of the stepsconsisting of shredding, filtering and spinning in the presence of from0.01% to 0.25% by weight based on the bone dry weight of the pulp of anadded mixed ether having attached to the ether oxygen a polyethyleneoxide radical with from 6 to 20 ethenoxy units and a cycloaliphaticradicalv selected from the group consisting of the dihydroabietyl,deh'ydroabietyl, tetrahydroabietyl and abietyl radicals.

6. The method of treating refined chemical pulp containing not more than0.15% ether extractable matter which comprises adding to the refinedchemical pulp from 0.01% to 0.25% by weight based on the bone dry weightof the pulp of ainixed ether having attached to the ether oxygen apolyethylene oxide radical with at least three ethenoxy residues and acycloaliphatic radical selected from the group consisting of thedihydroabietyl, dehydroabietyl, tetrahydroabietyl and abietyl radicals.

'7. The method of treating refined chemical pulp containing not morethan 0.15% ether extractable matter which comprises adding to therefined chemical pulp from 0.01% to 0.25% by weight based on the bonedry weight of the pulp of a mixed ether having attached to the etheroxygen a polyethylene oxid radical with from 6 to 20 ethenoxy units anda cycloaliphatic radical selected from the group consisting of thedihydroabietyl, dehydroabietyl, tetrahydroabietyl and abietyl radicals.

8. As a new article of manufacture, a refined 9 chemical pulp productcontaining not more than 0.15% of natural ether-extractable matter andhaving incorporated therein from 0.01% to 0.25% by weight based on thebone dry weight of the pulp of a mixed ether having. attached to theether oxygen a polyethylene oxide radical with at least three ethenoxyresidues and a'cycloali phatic radical selected from the groupconsisting of the dihydroabietyl, dehydroabietyl, tetrahydroabietyl andabietyl radicals. i

9. As a new articl of manufacture, a refined chemical pulp productcontaining not more than 0.15% of natural ether-extractable matter andhaving incorporated therein from 0.01% to 0.25% by weight based on thebone dry Weight of the pulp of a mixed ether having attached to theREFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Number 1 Bruson Nov. '7, 1939

